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BDRY.," and "CANADA" or "U. S." are cast in raised letters on the other three sides. In general these posts are set in solid ledge rock or in large bowlders along the banks of the waterways; and where such sites were not available, they were set either in granite blocks or in concrete bases 12 inches square extending to solid foundation below the frost line. Of the 256 boundary reference monuments between the source of the St. Croix River and its outlet in Passamaquoddy Bay, 243 are of this type. The remaining few reference monuments are of the bronze disk type (fig. 2) except reference monument 233 which is the center of Whitlocks Mill Lighthouse. The disks are 2 inches in diameter and one-fourth inch thick and are firmly held in place by a 4-inch shank split to take a metal wedge which expands the shank as it is driven into a drill hole in the rock. Two-inch and three-inch disks of this type were also used to mark triangulation and traverse stations and, in the tables describing

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Bronze post monuments used to reference the boundary along the St. Croix River

and defining the boundary line, many of these stations are included as additional boundary reference marks. Where ledge rock or large bowlders were not available, the disks were placed in the ends of granite posts 8 inches square and 3 feet long, set vertically so that the end containing the disk would be flush with the surface of the ground.

All of the above reference monuments are consecutively numbered from the head of Monument Brook to the mouth of the St. Croix River, and the monuments are so designated and shown on the boundary maps.

The range marks (fig. 3) on the shores of Passamaquoddy Bay consist of truncated pyramids of concrete which taper uniformly from a triangular base 6 feet on each side to a flat top of an area of about 1 square foot. The base extends 1 foot above and 3 feet below the surface of the ground, and the height of the pyramid above the top of the base is 6 feet.

The front side of each mark faces squarely in the direction of the boundary turning point or the boundary course which it ranges, and to increase its visibility has a coat of white cement. In the center of the front face is a manganese-bronze plate (figs. 4 and 5) which bears the words "UNITED STATES" or "CANADA" (depending on the location of the mark), the number of the range mark, the number of the boundary course or turning point which it ranges, and the words "TREATY OF 1908" (or "1910"). This plate is 4 feet below the top of the mark and is held in place by a pair of lug bolts screwed into the back of the plate and embedded in the concrete. The face of the plate is recessed into the concrete to a depth of 1 inch, and the concrete is beveled from the plate to the surface of the face of the mark.

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Bronze disks used as triangulation station marks, bench marks, and in a few places as boundary
reference monuments

The center of the range mark (the exact point to which the triangulation measurements refer) is marked by a hole in a copper plug set in the top of the mark flush with the surface of the con

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crete.

CONSTRUCTION OF
OF MONU-

MENTS

Along the St. Croix River sites could be chosen for reference monuments as a rule on large bowlders or outcrops of solid rock. Under such conditions the setting of a reference monument of the bronze-post or

bronze-disk type was a sim- Setting bronze post reference monument 85 in bowlder on Spednik ple operation. A hole was

Lake

drilled in the rock of sufficient diameter and depth to receive the shank of the disk or post and was then filled with neat cement mortar. A metal wedge was started into the split shank, which was then inserted in the drill hole, and the disk or post was driven home, the wedge spreading the shank and the cement filling every interstice.

Where solid rock or large bowlders were not available for monument sites, the reference monuments were set either in granite blocks or concrete bases. Where the granite blocks were used, an excavation 3 feet deep was made in which the post, 3 feet long and 8 inches square, was set and the excavation was filled in. A

Typical concrete range mark on Passamaquoddy Bay

bronze post or disk reference monument was then set in the top of the granite post in the manner before described.

Where concrete was used, a base 1 foot square was constructed in which to set the bronze reference monument. In solid ground the excavation for the base was carried only to a depth of 3 or 4 feet; but where the ground was swampy the excavation was made 5 feet or more in depth, and into the bottom several spruce or cedar poles were driven to hardpan. The tops of the poles, left projecting

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up into the excavation, were then nailed or wired together and the concrete was poured around them. The part of each base projecting above the surface of the swamp was narrowed down to a cross section 1 foot square, and in the center of this the bronze disk or post was set.

Range mark construction; first panel of form in place.

For the range marks on Passamaquoddy Bay a design for portable concrete forms was made by the United States Bureau of Lighthouses, and the forms, closely following these specifications, were built at Calais, Me.

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When the site of a range mark had been determined, reference stakes were first set in pairs, one pair on the line to the boundary turning point and the other pair at right angles to that line. Corner stakes were then set and the excavation for the foundation was dug, usually to a depth of not less than 3 feet. This excavation was filled with concrete to the level of the ground, when the baseboards were placed in position. As these inclosed the triangular base and thus fixed the position of the center of the structure, they had to be carefully centered, oriented, and leveled. When this had been completed, more concrete was added until it was flush with the top of the baseboards. The first panel of the form was then put in position on top of the baseboards, bolted together, and tied

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down to the base, when it also was filled with concrete. The top panel was then put in position and filled with concrete.

For the typical range mark the proportions of the concrete were 1 part Portland cement, 21⁄2 parts sand, and 4 parts gravel, a richer mixture being used where the mark was exposed to wave action or floating ice. Fresh water was always used in mixing the concrete. As the

Range mark construction; first panel filled and second panel being put in place

work progressed, large rocks were placed in the center of the concrete mass, care being taken that they did not come closer to the form than 3 inches. The concrete was thoroughly tamped into place and spaded on the sides.

When the concrete

was in place, the copper bolt, three-fourths inch in diameter and 4 inches long, for marking the exact center of the range mark, was set at the intersection of the two lines determined by the two pairs of reference stakes, using a theodolite to project the lines to their intersection.

The bronze plate, on which was marked the number of the range mark and the course or turning

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point which it ranged, was put in place as the placing of the concrete progressed. A 1-inch board with beveled edges, slightly larger than the plate, was fastened to the inside of the lower panel facing the boundary, in the proper position. The plate was then fastened to the board by means of copper nails, allowing the lug bolts on the back of the plate to be fixed in the concrete. When the form was removed after the concrete had set, the copper nails were pulled through the board and were then cut off flush with the face of the plate.

After the form was removed any rough edges at the joints between the panels

Specially constructed range mark on site exposed to floating ice

of the form were trimmed and rubbed smooth, and a coat of neat cement was applied to the range mark, using white cement on the front side of the mark to make this face of the structure more conspicuous at a distance.

At two places, Dog Island and Lubec Breakwater, where the range marks are on sites which in winter, at high tide, are exposed to floating ice, special precautions were taken to make sure that

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